The present invention generally relates to rotational control apparatus, relates particularly to clutches, and relates specifically to fan clutches.
Although fan clutches of the type shown in U.S. Pat. Nos. 3,253,687; 3,409,305; 3,762,517; 4,226,095; and 4,877,117 have proven to provide precise power, exceptional economy and dependable, long-lived durability, there exists a need to provide improvements to result in a further advantageous clutch. Specifically, a need exists to provide maximum engine cooling at both maximum engine torque and at maximum engine horsepower. Depending upon the particular design of the engine, maximum engine torque occurs typically at about 1200 RPM engine speed while maximum engine horsepower occurs typically at about 2100 RPM engine speed. To provide maximum engine cooling at both maximum engine torque and at maximum engine horsepower, the radiator cooling fan must run at a speed providing maximum air flow, typically at the speed of maximum engine horsepower, at both maximum engine torque and at maximum engine horsepower engine speeds. As the fan is often driven through a belt drive from the engine crank shaft and is typically selected to provide maximum air flow at the speed of maximum engine horsepower, a problem exists to also obtain maximum cooling at maximum engine torque speed which is considerably less than maximum engine horsepower speed.